Blended wing body (BWB) aircraft are being studied by governmental agencies, universities, and private industry for various applications, including passenger and cargo carrying applications. A BWB may be characterized as a hybrid shape that primarily resembles a flying wing, but also incorporates some features of a conventional aircraft. For example, FIG. 1 shows a conventional BWB aircraft concept 50 in accordance with the prior art. The BWB aircraft 50 includes an efficient, high-lift wing assembly 52, and a central, airfoil-shaped body 54. In the concept shown in FIG. 1, the BWB aircraft 50 includes three engines located in nacelles 56 mounted above the upper surface on pylons 58 near a trailing edge of the BWB aircraft 50. It is desirable to have engines with the highest possible ratio of fan-to-core airflow (bypass ratio) to increase propulsive efficiency. Studies by the National Aeronautics and Space Administration (e.g. research program FS-2001-04-24-LaRC published at http://oea.larc.nasa.gov/PAIS/BWB.html) and other research facilities suggest that a relatively large commercial BWB aircraft designed to carry approximately 450 passengers may advantageously consume 20 percent less fuel than comparable jetliners of today, while cruising at high subsonic speeds on flights of up to 7,000 nautical miles.
While BWB aircraft of the type shown in FIG. 1 may provide desirable results, there is room for further improvement. For example, as the bypass ratio of the engines of the BWB aircraft 50 is increased, the engines and nacelles 56 get bigger and heavier, which makes a low loss integration of the engines on the airframe more difficult, and which also adversely affects the weight and balance of the BWB aircraft 50.
More highly-integrated engine installations having inlets flush mounted on a surface of the BWB aircraft 50 may partially mitigate these adverse effects. The intent of such highly-integrated installations is to ingest a portion of a boundary layer flow that is built up on an upper surface of the BWB aircraft 50. Passing that portion of the boundary layer flow through the engines can improve the overall efficiency, however, a key concern of this approach is pressure distortion in the flow at the engine face (both the fan and core streams) and its resulting impact on engine operability. Also of concern is the shaping of the nacelles, and in particular the channels between the nacelles, to produce shock free and separation free flow so as to minimize drag. Therefore, unconventional integrated propulsion systems and methods for BWB aircraft which mitigate the installation problems discussed above and which can increase the overall capabilities of the engine/airframe system would have utility.